Quoting Bruce Coston (jane_ikari at yahoo.com):
> I hope that Val Henson's occasional atime gets put in the filesystem
> automatically vs. noatime or atime . I prefer to get most of the
> benefits of atime while avoiding most of the cost , and may bother
> specifying my atime preference when I have enormous time to waste .
Overhead of atime updating isn't[1] all _that_ big a problem except
(arguably) when running on battery power -- though one can usefully
experiment with doing "noatime" and "nodiratime" on parts of the tree,
and it does have significant benefits on my server. (Some places in the
file tree, the atime time stamp doesn't matter at all.)
Anyway, Val now goes by _Valerie Aurora_, and she calls what you're
referring to her "relative lazy atime patch", sometimes referred to as
"relatime". See: http://valerieaurora.org/patches.html
I like it; smart idea. She notes that the -mm kernels now include the
patch (probably assembled by Ingo Molnar, based on her work).
/usr/bin/mount also requires a patch, if you use it.
As of a couple of years ago, Torvalds seems to have been saying "no",
though he wavers a bit: http://kerneltrap.org/node/14148 One of the
obstacles he cites is that distro kernels' "mount" utilities don't
support it, ye olde chicken-and-egg problem. Also, it's technically a
violation of standards. Ingo Molnar and others are arguing for it being
included but defaulted to off, which skirts various problems (but Alan
Cox objects strongly to even that much change).
Tidbit from Andrew Morton in the cited kerneltrap.org thread: "noatime
is a superset of nodiratime, btw."
[1] In my own experience, where my usage isn't I/O-intensive. Views
Differ.<tm>